#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>

int sum(int x)
{
	if (x == 0)
	{
		return 0;
	}

	x + sum(x - 1);
}

int main()
{
	int x;
	scanf("%d",&x);
	int y = sum(x);
	printf("%d\n",y);

	return 0;
}